Some experimental observations on the single and multi-phase flow patterns in a model flash evaporation chamber

Flow characteristics inside a model flash evaporation chamber for Multi-stage Flash (MSF) desalination have been investigated using Particle Image Velocimetry (PIV). The back flow region near the inlet gate, the free water surface shape, and the overall velocity distribution were measured so as to identify the characteristics of the flow pattern at different water levels in the chamber. The results show that a large recirculation region with several vortices embedded would be generated at a higher water level (approximately twice the inlet gate height). The water level remained uniform in spite of the presence of the vortices. Three flash evaporation modes at different superheats of the water in the flash chamber were also studied using a high speed CCD camera. The bubble behaviors such as the size, velocity, and growth rate were estimated and analyzed. It was found that the multi-phase flow pattern during the flash evaporation was mainly determined by the liquid superheat and the nuclei distribution. Flow characteristics inside a model flash evaporation chamber for Multi-stage Flash (MSF) desalination have been investigated using Particle Image Velocimetry (PIV). The back flow region near the inlet gate, the free water surface shape, and the overall velocity distribution were measured so as to identify the characteristics of the flow pattern at different water levels in the chamber. The results show that a large recirculation region with several vortices embedded would be generated at a higher water level (approximately twice the inlet gate height). The water level remained uniform in spite of the presence of the vortices. Three flash evaporation modes at different superheats of the water in the flash chamber were also studied using a high speed CCD camera. The bubble behaviors such as the size, velocity, and growth rate were estimated and analyzed. It was found that the multi-phase flow pattern during the flash evaporation was mainly determined by the liquid superheat and the nuclei distribution.